The technique of dynamic ultrasonography is enabling both obstetricians and psychologists to improve their assessment of health of the fetus, including quality and activity of the fetal central nervous system. It is now known from dynamic ultrasonography that healthy human fetuses make movements from 7 weeks of gestation onward, and that 15 distinct patterns of movement (eg, breathing, swallowing, sucking) emerge at between 8 and 15 weeks. 1 Visser GHA Mulder EJH Prechtl HFR Studies on developmental neurology in the human fetus. Dev Pharmacol Ther. 1992; 18: 175-183 PubMed Google Scholar Fetal behavioral states develop gradually from around 28 weeks of gestation and are fully developed at about 36 weeks. 2 Nijhuis JG Prechtl HFR Martin Jr CB Bots RSGM Are there behavioral states in the human fetus?. Early Hum Dev. 1982; 6: 177-195 Summary Full Text PDF PubMed Scopus (685) Google Scholar Deviations from these trends suggest an abnormality. For example, fetuses of mothers with type 1 diabetes show a 1–2 week delay in the emergence of almost all movement patterns, poorer concordance among indices of behavioral state (such as heart rate, body movements, and eye movements), more frequent asynchronous and disrupted transitions between behavioral states, and shorter rest activity cycles than comparably aged fetuses of nondiabetic mothers. 3 Mulder EJH Visser GHA Bekedam DJ Prechtl HFR Emergence of behavioral states in fetuses of type-1 diabetic women. Early Hum Dev. 1987; 15: 231-251 Summary Full Text PDF PubMed Scopus (105) Google Scholar , 4 Visser GHA Bekedam DJ Mulder EJH van Ballegooie E Delayed emergence of fetal behavior in type-1 diabetic women. Early Hum Dev. 1985; 12: 167-172 Summary Full Text PDF PubMed Scopus (28) Google Scholar , 5 Robertson SS Dierker LJ The development of cyclic motility in fetuses of diabetic mothers. Dev Psychobiol. 1986; 19: 223-234 Crossref PubMed Scopus (21) Google Scholar